Well, the site that's selling them tells you what they'll do... though they might not be coming true with the statement "These kits do not affect high speed stability." - especially with a 50mm (~2 inch) tail lift. They do increase handling sharpness and this invaribly come at the cost of being more nervous in a stright line, especially at elevated speeds.
A 50mm change will render your centerstand useless, if you care. 35mm is a safer way to go and should still permit the centerstand to work (I know it does on a 2G B12 anyway), though the ground better be flat. There is a thread in the FAQ on how to make your own dogbones.